Method of drying material



Nov. 10 1925. 1,560,589

B. R. ANDREWS ET AL METHOD OF DRYING MATERIAL Filed May 25. 1922 Inuentors. Bernard R. Andrews Stanley R Lovell byi'uwa Maw Any5.

Patented Nov. 10, 1925.

UNITED STATES BERNARD B.

ANDREWS, BBAINTBEE,

AND STANLEY I. LOVELL, OF BBOCK'ION- MASSACHUSETTS.

mnon OF DRYING MATERIAL.

Application filed Kay 25, 1922. Serial No. 588,481.

To all whom it may concern:

Be it known that we, BERNARD R. AN mmws, a citizen of the United States, and resident of Braintree, county of Norfolk,

State of Massachusetts, and STANLEY P. Lovnnn, a citizen of the United States, and resident of Brockton, county of Plymouth, State of Massachusetts, have invented an Im rovement in Methods of Drying Materia of which the following descri tion, in connection with the accompanying rawing, is a specification, like 0 aracters on the drawing representing like parts.

This invention relates to a method of drying, or evaporating liquid from, material and it has articular reference to a method adapted or use in drying material which contains or is provided with a coating of a li uid which has a constituent of such volatihty that the evaporation of such constituent reduces very materially the temperature of the material.

In the industrial arts it is frequently necessary to treat some material with a l quid having a highly volatile constituent either for the purpose of impregnating or coating said material with this liquid.

It is also frequently necessary to dry the material after it has been thus impregnated or coated and under some circumstances the drying should be done without bringing the treated material into contact with a hard heated surface because of the injury to the finished product which will result by such procedure.

Further it is often necessary to perform the drying operation without reducing the temperature of the material to such a point that there is danger that moisture of condensation from the atmosphere will gather on the cooled material. The evaporating of a highly volatile constituent from any material rapidl reduces the temperature of the material an under some circumstances this reduction is such as to carry the temperature of the material below the dew-point of the surrounding atmosphere. When this condition arises moisture in the atmosphere will be condensed by the material. As stated above there are certa n lines of manufacture in which the gathering of moisture of condensation on the material has a deleterious efiect thereon, as

the cooled material and moisture of condensation will gather on well as necessitating the reevaporation of the condensed moisture.

Merely as illustrating some manufacturing processes in which the above operations take place I might refer to that of forming shoe counters or box toe blanks by impregnating felt, fabric or similar material with a stiffening agent in liquid form and containing a volatile solvent such as alcohol, gasoline, naphtha, etc, and subsequently drying the material to evaporate the solvent and leave the stiflcning constituent in the material for the purposeof providing the desired stiffness. Another illustration is that involved in coating material with some emulsion or liquid coating containing a volatile constituent, and subsequently drying the coated material to evaporate the volatile constituent whereby the coatin on the material becomes solid. These, owever, are simply illustrations of industrial-art rocesses to which our invention is applicab e.

As stated above it is an object of our invention to provide a novel process for drying material which has been impregnated or coated with a liquid containing a volatile constituent by which the drying operation can be carried out without reducing the temperature of the material below the dewpomt temperature of the surrounding atmosphere thereby avoiding possibility of water of condensation collecting on the dried material.

Another object of the invention is to proylde an improved process by which this drymg operation can be carried out without bringing the material to be dried in contact with any solid substance, suchfor instance as a drying drum, which would be likely to injure in any way the material being treated.

The invention further has for its object to provide an improved method of drying material having various other features all as Wlll be more fully hereinafter set forth.

In order to give a better derstanding of our invention we have illustrated more or less diagrammatically in the drawin one apparatus by which the method may e carried out, but we wish to state that the practise of the invention is by no means limited to any particular apparatus-nor to the drying of any particular material.

'In the drawings, Fig. 1 is a sectional we have shown two air view illustrating a device for drying web material in accordance with our hereinafter described method.

Fig. 2 is a section on the line 2-2, Fig. 1.

Fi 3 is a view showing another way 1n whic the method may be practised.

As stated above our invention is particularly applicable for drying material wh ch has been impregnated or coated with a l 1quid having a constituent of such volatil ty that in the ordinary evaporating operation the temperature of the material will be reduced below the dew point of the surrounding atmosphere.

In carrying out our invention we provide means for maintaining the temperature of the material above the dew-point temperature of the surrounding atmosphere dur ng the drying operation and without maintaining said material in contact w1th any solid substance. Furthermore the material is maintained at this desirable temperature without regard to the temperature of the atrrliosphere directly adjacent to the materia One way in which this result can be accomplished is by subjecting the material to the action of radiant heat and at the same time passing a current of air across the material for assisting the evaporating process. Another way in which this end might be accomplished would be to float the material on a heated liquid while subjecting the material to the action of a drying current.

In Figs. 1 and 2 of the drawings we have illustrated somewhat diagrammatically an apparatus adapted to operate on the rinciple of subjecting the material to be ried to the action of radiant heat during the drying operation thereby to maintain said material at the desired temperature.

In said figures the material to be dried is indicated at 1 and may be in the form of a web or a sheet. 2 and 3 indicate two heating chambers spaced apart to form between them a space 4 through which the material to be dried may pass. Means are rovided for delivering a current of air or ot er drying medium across both sides of the material while it is passing, or located between, the drying chambers 2 and 3 and as illustrating one way in which this may be done ducts 5 each having a delivery nozzle 6 arranged to direct an air current over one face of the material 1.

ere two nozzles 6 are employed, one on each side of the material, both sides of the material will be subjected to the action of the drying current. Each of the heatin chambers 2 and 3 has within it a heater 0 some sort, herein shown as steam. pipes 7. Each of the chambers 2 and 3 will preferably have all sides thereof except that adjacent the material 1 formed of mi ble heat insulating material, and the sides adjacent the material 1 are formed of a material which will transmit radiant heat freely but will not transmit heat by conduction to any extent. This can be accomplished by mak-.

ing the sides 8 of glass and by double glazing the sides the amount of heat by conduction is practically nil while radiant heat will be freely transmitted.

In using this apparatus for drying material the latter is placed in the space 4 between the two heatlng chambers and is subjected to the action of the drying medium delivered through the nozzles 6. At the same time the steam coils 7 are utilized to generate heat in the heating chambers 2 and 3 and heat of radiation will be transmitted freely through the glazed sides 8 onto the material 1 thus heating the latter. amount of heat which is generated in the steam coils will be suflicient so that the radiant heat will be received by the material 1 in suificient uantities to maintain the temperature of t e material above the dew-point temperature of the surrounding atmosphere.

ere the material 1 is coated or impregnated with a liquid having a volatile constituent the evaporation of this volatile constituent will, of course, reduce the temperature of the material 1 and by properly regulating the amount of heat radiated from the steam coils it is possible to maintain the temperature of the material 1 above the dew-point temperature thus obviating the possi ility-that any moisture of condensation from the atmosphere can gather on the material. Furthermore by using the two nozzles and delivering a current of drying medium against the material 1 the latter can be carried through the space 4 without appreciable contact with any heated support or rest, and, therefore, it is possible to use this method and apparatus in drying web material of a character which will be iniured by being brou ht into contact with a eated solid 0 feet d uring the drying operation.

The material 1 being dried may be fed through the space 4 or may be placed there in and allowed to remain for a proper length of time and then removed therefrom.

In Fig. 3 we have shown diagrammatically another way in which the invention may be practised. In said filgurefi re resents a vessel containing some quid 10 such as mercury and 11 indicates suitable meansfor heating the liquid. 12 indicates a nozzle which is movable over the li uid 10 to flow thereon a or web 13 of e material to be dried which may be in liquid or semi-liquid form. A suitable drying medium may be lfJlOVilfi over the wefbd13 front1hthle agzzles T1114 or epurposeo rymg e a r. e mercury or other liquid 10 be mane before it is used in the drying operation so that the drying will be done with air that contains no moisture that can condense. This method of drying involves the use of a ver expensive apparatus for thus dehumi ifying the air and this isone disadvantage resulting from said method.

Another method which is now commonly used for drying such material is to retard the drying operation by carrying it on an atmosphere highly saturated with the vapor of the solvent, as under such circumstancesthe evaporation will take place slowly and there will be a correspondingly small reduction in temperature due to such evaporation. This method, however, has the disadvantage that it involves considerable fire hazard. In order to avoid both of the above difiiculties it has been proposed to use in certain industrial arts solvents having a high boiling point so that in order to evaporate the solvents com letely a temperature must be used which is a ove any dew-point temperature of the surrounding atmosphere. This, however, is not satisfactory because of the high cost of such solvents.

An advantage inherent in our improved method is that the desired drying operation can be carried out at a relatively small expcnst'. and without the necessity of em 'iloying an expensive apparatus for dehydrating the a i r. Fu rthermore our method can be carried out without any lire hazard because a suflic'n-nt amount of air may be used at all times to keep the vapor which is floated from the material diluted below the ignition point.

'1- dcsire to state that the apparatus which is diagrannnatically. shown herein has lwcn used merely for the purpose of illuslrating how the method might be practised 2! ud without any intent to limit the invention In any particular apparatus.

I claim.

I The steps in the method of drying malvrial carrying volatile liquid which consist lll evaporating said liquid from the material at such a rate as would normally cause a rm'luction of the temperature of the material below the dew-point of the surrounding atmosphere, and maintaining the material at a temperature above said dew point by radiant heat.

2. The steps in the method of (1 ing material carrying volatile liquid whic I consist in evaporating said liquid from the material at a sufliciently rapid rate to cause normally a reduction of the temperature of'the material below the dew-polnt of the surrounding atmosphere, and maintaining the material at a temperature above said dew point without contact with a solid heated surface.

3. The steps in the method of drying material which carries a volatile liquid, which consist in passing an air current over the material and thereby producing evaporation of said liquid from the material at sucha rate as would normally cause a reduction of the temperature thereof below the dew-point of the surroundingatmosphere, and subjecting said material to the action of radiant heat in sufiicient quantities to maintain the material at a temperature above said dewpoint.

4. The steps in the method of drying material which carries a volatile liquid, which consist in evaporating in a space open to the atmosphere said liquid from the material at such a rate as would normally cause a reduction of the temperature of the material below the dewoint of the surrounding atmosphere, an maintaining the material at a temperature above said dew-- point by radiant heat.

5. The steps in the method of drying material which carries a volatile liquid, which consistin passing an air current over the material at a rate to cause normally by said evaporation a reduction in the temperature of the material to a point below that of the air current and below the dew-pointof the surrounding atmosphere, a nd subject-ing said material to the action of radiant heat in suflicient quantities to maintain the material at a temperature above said dew-point.

6. The steps in th method of drying inatcrial carrying a volatile liquid, which consist in evaporating said liquid from the material at such a rate as would normall cause a reduction in the temperature of t io material below the dew-point of the surrounding atmosphere, and maintaining the material at a temperature above said dewoint by radiant heat as'distinguished from eating by conduction.

In testimony whereof, We have signed our names to this specification.

STANLEY P. LovELL. BERNARD R. ANDREWS. 

